The present invention relates to an electron gun component for a color television picture tube. In a television picture tube the electron beam generating emissive cathode must be heated to a finite temperature sufficient to produce a stream of electrons before the picture is visible upon set turn-on. A variety of schemes have been employed to reduce this on-set of electron emission, such as by continuously heating the cathode filaments to maintain the emissive portion near the temperature which will produce sufficient electron emission. Such systems are wasteful of energy in that they remain on even while the set is effectively not operating, and such systems have been criticized from a safety viewpoint. An alternative system has been proposed in which the emissive portion of the electron gun cathode has a low mass and is isolated from the rest of the electron gun body to limit thermal conduction away from the emissive portion and enable it to be heated with a minimum power input. Such electron gun components are shown in U.S. Pat. Nos. 3,333,138 and 3,354,340. In both of these prior art electron gun structures a cathode is shown in which an emissive cathode portion is spaced from the rest of the electron gun body by a plurality of thin, low thermal conductivity support members.
The positioning and spacing of the electron emissive cathode portion in such electron guns is very critical and any support system for spacing and supporting the emissive portion must provide sufficient rigidity and structural stability to insure that the alignment and spacing of the emissive portion is maintained. Improper alignment or spacing of the emissive portion can result in formation of poor picture clarity and discrimination.
In the aforementioned U.S. Pat. No. 3,333,138 the support strap structure is an elongated V-shaped body which extends well beyond the supporting sleeve within which the emissive cathode portion is disposed. In U.S. Pat. No. 3,354,340, the support sleeve is provided with a flanged surface to which the support strap end portion is welded and also the emissive cathode portion has a flange portion for connection to the support strap structure.